3,499,887 United States Patent Office Patented Mar. 10, 1970 2 tained from a divalent metal such as zinc, cadmium and 3,499,887 POLYMERIZATION CATALYSTS FOR copper with ethane dithiol (i.e. R1 is a di-methylene EPSULPHOES group and Y is sulphur) or bis (beta-mercaptopropyl) Wilfrid Cooper, Aldridge, George Vaughan, Sutton Cold Sulphide (i.e. R1 is -CHCH (CH) SCH(CH) CH field, and Reginald T. Wragg, Tamworth, England, as and Y is Sulphur). In the case where R contains an atom signors to The Dunlop Company Limited, London, which is associated with the metal as by means of a co England, a British company ordination bond (->), the compounds can be represented No Drawing. Filed Apr. 28, 1967, Ser. No. 634,476 by the general formula Claims priority, application Great Britain, May 13, 1966, 21,239/66 S Hnt. C. C07d 23/00; C07f 3/06, 3/08 10 U.S. C. 260-239 4 Claims Z. -(^^ Y. ) where A is equal to 0, 1, 2 . (Az--B-1), Az--B ABSTRACT OF THE DISCLOSURE where B is an integer greater than 0, X represents a group 15 containing an atom such as nitrogen, oxygen, sulphur or Organometallic compounds suitable as catalyst for the phosphorus capable of forming a co-ordination bond polymerization of episulphides, in which at least one of with the metal and RX is equivalent to R. Particularly the valency states of the metal is satisfied by the grouping Suitable catalysts of this type are compounds in which Ais -SR where R represents an organic radical containing 0 and B is 2 and M is a divalent metal i.e. compounds of at least one other atom which is chemically bonded to 20 general formula the metal or which is associated with the metal by means of a co-ordination bond, are prepared by reacting a salt X S of the metal with the appropriate thiol compound. R? YM/ Y, N/ R / S X 25 This invention relates to the polymerization of episul The group X in the above general formula may be phides. for example an -OR2 group, an -SR3, an -NCRRs) The present invention provides organometallic com group or a P(R6Rf) wherein said groups R2, R, R R5, pounds suitable as catalysts for the polymerization of R6 and R7 represent hydrogen atoms, alkyl groups, cyclo episulphides, in which one or more of the valency states 30 aliphatic groups, aryl or aralkyl groups. The simplest of the metal are satisfied by the grouping-SR where R compounds of this type are those in which X represents represents an organic radical containing at least one a hydroxyl group or an amino group. These simple other atom which is chemically bonded to the metal compounds are generally insoluble in the episulphide or which is associated with the metal by means of a monomer or monomers to be polymerized and in most co-ordination bond. (Hereafter these compounds will be 35 common solvents. However, by substituting alkyl or referred to as “catalysts.") other hydro-carbon groupings onto the nitrogen, sulphur The present invention also provides a method for the or other co-ordinating atom, the compounds can be made polymerization of one or more episulphides which com Soluble in the monomer or monomers to be polymerized prises contacting the episulphide or episulphides with or in the solvent and these soluble catalysts are partic these organometallic polymerization catalysts. 40 ularly useful in that they enable control to be exercised Particularly suitable catalysts are compounds. in which over the molecular weight of the resulting polymers. Par the metal has a co-ordination number of 4, 5 or 6 in ticularly preferred, are compounds in which X is complexes with ligands containing sulphur and/or other -NRRs where one or both of R and R5 are the same donor atoms. Examples of such metals are zinc, cadmium, or different alkyl groups having 1 to 4 carbon atoms. copper, silver and nickel but certain other metals, e.g. 45 Examples of Suitable catalysts of this type are the com lead can also be employed. The particularly preferred plexes obtained from a metal salt and, for example, beta catalysts are those which contain zinc or cadmium as the aminoethane thiol, (gem-dimethyl) beta-aminoethane thiol metal. Not all the valency states of the metal need be (i.e. R1 is -CH2C(CH3)2-) or beta-mercapto etha satisfied by the chemical bonds to the -SR grouping as no ethanol (i.e. Ri is -CH2CH2-) N-n-butylaminopro described above. The catalysts have the general struc 50 pane-2-thiol or N-di-n-butyl aminopropane-2-thiol (i.e. ture ZA-M-(S-R) where M is the metal, Z is an R1 is -CH2CH(CH3) -). The last two named com anion such as Cl, CH3COO or CO - and A is equal pounds are catalysts which are soluble in the monomer(s) to 0, 1, 2 . (Az--By-y), (Az--By), where z is the or in hydrocarbon solvents. valence of the anion and y is the number of atoms or For convenience most of the structural formula are groups in the -S-R grouping which are chemically 55 depicted in the monomeric form in which the group X bonded to the metal M. The group R of the polym or Y is linked to the same metal atom as the sulphur. erization catalyst can be an aliphatic cycloaliphatic, Analytical and molecular weight data generally support heterocyclic, aryl or aralkyl radical but must contain a these structures. It is possible, however, for more than second atom or grouping which is either bonded or co one metal atom to be attached in the complex and thus ordinated to the metal atom M. In the case where R con 60 result in dimeric and higher polymeric structures such as tains an atom or grouping, Y, such as S or COO, which s-R-Y YMSR 1. is chemically bonded to the metal M, such compounds ZAM M. Z.A or - ra can be represented by the general formula / ZA Y-R-S S / N 65 The polymerization catalysts can be prepared by re ZA-M R acting a salt of the metal such as the oxide, chloride or () ) acetate of the metal with the appropriate thiol compound in which A is equal to 0, 1, 2 . (Az--2B-2), preferably in the presence of an acid-acceptor. The thiol Az--2B where B is an integer greater than 0 and is usually compound must contain in addition to the thiol group a equal to 1, and RY is equivalent to R. Examples of suit 70 further atom which can become bonded directly or by able catalysts of this formula are the compounds ob means of a co-ordination bond to the metal. This further 3,499,887. 3 4. atom can be for instance a sulphur atom in the form of a mercaptains, in the reaction mixture is detrimental to the second thiol group to yield catalysts of formula control of molecular weight by catalyst concentration and when high molecular weight polymers are required they should be rigidly excluded. Mercaptans or compounds which can react with the 3. episulphide to yield mercaptans, such as for example As described hereinbefore they may also be dimeric or amines, can be used as transfer agents. Added in con polymeric in structure. In the case where the catalyst con trolled amounts they result in a lowering of the molecular tains an atom which co-ordinates with the metal rather weight of the polymer without any change in rate of than becomes directly bonded then the metal salt is re O polymerization. The amount to be added to produce a acted with for example an amine-thiol given molecular weight will of course depend upon the nature of the mercaptan used and on the amount of catalyst used. or an ether thiol (RO-R-SH). Usually in this case It is believed that the polymerization catalyst is in two moles of the amine-thiol or ether-thiol will react with corporated into the growing polymer chain and provides one mole of the salt of a divalent metal. the active centre at which growth of the polymer chain The reaction between the metal salts and the thiol occurs. Growth of the polymer chains continues until compounds to prepare the catalysts can conveniently be all the available monomer has been polymerized and the carried out at room temperature (10 to 30° C.) simply resulting polymer chains contain the active centre pro by mixing the reagents in the presence of an acid ac vided by the catalyst incorporated therein. This active ceptor such as sodium hydroxide, Sodium bicarbonate, Or centre is stable and even after a period of several weeks ammonia, and stirring the mixture. The catalysts are addition of a further amount of monomer to the polym stable and can be stored for several weeks prior to use. erization reaction mixture will result in polymer-chain The amount of the metal salt and the thiol compound growth to increase the length of the existing polymer used can vary considerably but the molar ratio of the 25 chains. The present invention therefore provides a method metal salt to the thiol will preferably be from 1:1.5 to of making block copolymers of episulphides since the 1:2.5, usually 1:2 especially with zinc and cadmium salts. monomer added to an existing polymer containing an The polymerization of one or more episulphides using active centre may be a different monomer to that initially the catalysts can be carried out in the bulk phase or if added to the catalyst.